Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may be used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle.
The security controller typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition. A typical security system also includes a receiver associated with the controller. The receiver cooperates with one or more remote transmitters typically carried by the user and which are used to arm and disarm the vehicle security system, for example. Other remote control features, such as locking or unlocking vehicle doors may also be performed.
A typical security system switches from armed to disarmed modes responsive to the remote transmitter, and generates an audible chirp as confirmation to the user that the controller has changed modes or has at least received the signal to change modes. A synthesized voice message and/or a flashing of the vehicle lights may also accompany the chirp as confirmation. In some situations, it may be desirable to avoid the audible chirp, such as to avoid disturbing others in the vicinity of the vehicle, for example. This is generally described as "silent" arming or disarming.
A security system sold as the model AL-800 by a leading aftermarket vehicle security system provider, Omega Research & Development, of Douglasville Georgia, provided a version of this enhanced feature of selectable silent arming and disarming. The remote transmitter included an arm/disarm switch which when pressed rapidly twice in succession would cause silent toggling of the controller to the other mode. If pressed once for a normal length of time, that is, about one second, the normal toggling would occur with the audible confirmation chirp. If pressed longer than the fraction of a second, or if the first or subsequent transmission were not received, difficulties could arise in operating the silent arming and disarming. Difficulties can be due to outside radio interference causing an otherwise normal length signal to be received as two separated signals causing the unintentional toggling. Of course, two signals could be transmitted, but only one received due to interference.
Another somewhat more cumbersome approach to silent arming and disarming is disclosed in U.S. Pat. No. 5,534,845 to Issa et al. In this approach, the trunk release is pressed for less than a preset time of 2.5 seconds and then one of the separate arm or disarm switches on the remote transmitter is operated within a five second window for respective silent arming or disarming. Unfortunately, operating multiple switches in such a precise pattern may be difficult for some users. In addition, the user is not always confident that the first short trunk release pulse has been received by the controller. Accordingly, the audible confirmation chirp may be given even when undesired.